Method of molding lightweight concrete panels



Sept, l2, 1950 H. B. HAYES uETHon oF nomme ucmwnamm CONCRETE PANELS Filed Dec IN V EN TOR.

HAIL. B. HAYES Patented Sept. l2, 1950 PATENT OFFICE METHOD OF HOLDING LIGHTWEIGHT CONCRETE PANELS Halv B. Hayes, Tujunga, Calif., assignor to Hayes IEconocrete Corporation of America, Reno, Nev., a corporation of Nevada Application December 18, 1945, Serial No. 635,838

3 Claims.

This invention relates to a method of producing a building element.

In constructing buildings made of cementitious materials it is desirable to form walls which have suitable load supporting strength and which also possess heat-insulating qualities. It has been found that if a wall is constructed of solid cement of a thickness to be load-sustaining, and at the same time to comply with the limits of wall thicknesses as defined by building ordinance requirements, the wall will not have the desired degree of heat-insulating properties to prevent the formation of water condensate upon the inner wall surfaces, since under certain climatic conditions these surfaces will be at a temperature below the dew-point. In order to provide a cementitious wall which will not lbe subject to the foregoing condition it is necessary to incorporate heat-insulating material in the construction of the wall. Various attempts have been made to construct cementitious walls by the use of lightweight aggregate or a cementitious mass which has been expanded by the introduction of air or the creation of gas through the mass in a. chemical action. It is obvious that thin walls which can be prefabricated in a practical manner will not possess both insulation and strength. It is necessary therefore to supply strength to such insulating material in order to produce a wall having limited thickness and which possesses strength and heat-insulating qualities. In the present invention this is accomplished by forming a center core of heat-insulating material which leither includes light-weight aggregate or expanded cementitious material within which reinforcing members are imbedded and over the surface of which outer coatings of cementitious material are applied to provide compression strength for the structure. In order to insure that an effective bond will be created between the heat-insulating core and the outer coatings of strengthening material it is desirable to treat the core in a manner to increase the bonding surface thereon and to produce fissures inthe surface into which the coating material will become keyed. The wall sections are preferably made in panels which may be transported to a building site. When a core section of expanded cementitious material is made within which chemical reaction creates a gas tending to render the material foraminous it has been found that the sizes of the foramina vary throughout the cross-section of the core. In such a case the core when set will tendl to warp due tothe fact that the foramina adjacent to one face of the slab are of different size from the foramina on the other face of the slab. It is desirable that a method and means be provided to insure that the foramina shall be substantially uniform in size through the mass. This produces a slab of cementitious material which is of uniform 5 strength throughout and which when set will not warp. It is the principal object of the present invention. therefore, to provide a method of producing a heat-insulating core to which may be bonded flrmly cementitious coatings by which the structure will be made load and form sustaining, and whereby maximum strength and heat-insulating qualities will be obtained in a light-weight panel'of normal wall thickness.

It is another object of the present invention to provide a, method of treating an expanded heat-insulating cementitious core to insure that the fcramina occurring therein will be substantially uniform in dimension.

The present invention bontemplates the making of a core for a panel from expanded cementitious material or cementitious material containing light-weight aggregate, the panel carrying imbedded` reinforcing means and treated to produce surface fissures in its opposite faces capable of receiving a coating of water-proofing material or a. coating of cement whereby the structure may be used in a wall or partition.

The invention is illustrated by way of example in the accompanying drawings in which:

Figure 1 is a. diagrammatical view showing the flow plan and the apparatus through which the cementitious panels are passed initially.

Fig. 2 is a, flow plan showing the remainder of the apparatus through which the panels pass during the final stages of their treatment.

Fig. 3 is a view in plan showing one of the forms within which a panel is cast.

Fig. 4 is a view in transverse section through a mold as seen on the line 4-4 of Fig. 3 and shows the initial position of the reinforcing material therein.

Fig. 5 is a fragmentary view in section through a mold showing the manner in which the cementitious material increases in volume in the ilrst stage of the heating operation.

Fig. 6 is a view similar to Fig. 5 showing the manner in which the cementitious material is treated to produce a panel of uniform thickness.

Fig. 7 is a view in transverse section through a form showing the manner in which the cementitious material tends to crack in planes normal to the longitudinal plane of the reinforcing material due to forced drying and setting of the material.

Fig. 8 is a view showing one of the panels after it has been removed from the frame and is disposed vertically, and indicates the manner in which the bonding cracks act to receive an outer cementitious coating when the panel is used in a building structure.

Fig. 9 is a fragmentary view in section showing a form of panel having a multiple outer coating.

Referring more particularly to the drawing, III indicates a cement mixer of any desired construction. Within this mixer is placed a cementitious mass comprising Portland cement, clay, ne sand, bentonite, concrete sand, and a proportion of powdered aluminum and an alkaline hydroxide. These ingredients when mixed with water will make a light-weight porous cement due to the character and proportions of the ingredients as well as the action which will be produced by the powdered aluminum and the alkaline hydroxide in creating a. gas which will permeate the mass and will percolate therethrough to give the mass porosity and light weight. Disposed beneath the discharge spout II of the mixer I is a trackway I2 along which small trucks I3 may pass. This trackway extends through an initial expansion kiln I4, during which time the truck will carry molds I5. The truck is fitted with a clamping element I6 which may engage a cable I'I. The cable I1 is led around a pulley I8 at one end of the track and a pulley I9 at the opposite end of the track I2'. Suitable driving means 20 is provided adjacent to the pulley I9 to drive the cable I1 so that when a truck I3 is secured thereto -by the clamp I6 the truck will be drawn through the expansion kiln I4 at any desired rate ofspeed. The expansion kiln I4 may be of any desired length and is provided at its opposite Lends with doors 2| and 22 which may be lifted to permit entrance and exit of the truck I3. The kiln I4 may be heated -by any desired heating means, such as by hot air from a furnace, gas burners, or the like. It may be practical to equip the kiln with a plurality of infrared heating units 23 which may be disposed in any desired position within the kiln. It has been found preferable to dispose the heating units 23 beneath the track I2 and trucks I3 so that the greatest degree of heat will be at the bottom of the forms I and thus beneath the mass lof cementitious material therein. The forms I5 may be rectangular in shape and of any suitable dimensions, both as to surface area and as to thickness. It is intended that forms shall be of a shape and thickness vto define a wall panel when they process has been completed by first expanding the cementitious material and thereafter compacting it to reduce its volfume to a desired thickness, and to reduce the size of the foramina therein as produced by the gas bubbles.

For present purposes it has been found that a' mixture of cementitious material in the following proportion is suitable:

When this material is mixed in the cement mixer I0 it will produce a, slurry with which the form I5 is filled. When the truck I3 with the filled form is drawn into the expansion kiln I4 it will be subjected to a temperature of the order of 1D0-150 F. This temperature is produced by the dry heat developed by the heating units 23. The driving structure 20 for the pulley I9 is adjusted so that a desired chemical reaction will take place in the mass of the action 0f the aluminum powder, alkaline hydroxide, and water to form a hydrogen gas. Due to the fact that the gas forming agent will be more active when heat is applied the foramina at the bottom of the mass will be larger in size than the foramina at the center of the mass. This tends to offset the action of the gas to rise and create larger foramina at the top of the mass. However, suilicient gas does percolate through the mass to cause the foramina in the top surface to be larger than the foramina found at the bottom of the mass. This condition will be corrected byv a rolling operation to be hereinafter described. In actual practice it is found that the mass of material will be expanded to approximately twice the volume it possessed when in slurry form. When this action takes place the mass of material will rise above the top of the form a considerable distance. The degree of expansion of the mass will be controlled by the length of time the truck I3 remains within the expansion kiln and the amount of heat to which it is subjected while in the kiln, as well as the amount of water and expanding agent used. This expansion will be in direct proportion to the chemical consistency of the mass and the degree of heat applied. Normally the length of time is from fifteen to sixty minutes depending upon the thickness of the panels which are being formed. The track I2 extends beyond the exit end of the expansion kiln I4 a suilicient distance to Permit the truck I3 to be withdrawn completely from the kiln I4. When at this station it will be found that the mass of cementitious material indicated at 24 will be at a height above the top of the form-I5.

In processes heretofore practiced and in which cements of the general character here described were used it has been the common practice to scrape or otherwise remove the surplus portion of expanded material which had risen to a height higher than the level of the top plane of the form I5. It has been found that in attempts to cut or scrape the surplus material from the top.

of the form there is a tendency for the surface of the material to be torn or unduly roughened. This of course is due to the fact that the material has now attained a semi-solid or crust-like condition and chunks of the material are engaged by the scraping member and may be dragged acre-ss the surface in the plane of the cut. 'I'hls will tend to collapse the porous structure. In some instances a cover board has been placed on top of the material. This is objectionable due to the fact that portions of the upper surface of the cementitious mass will adhere to the board and will be withdrawn with it. This will of course produce a rough and undesirable pitted surface.

It has been found that the finished product may be greatly increased while maintaining its uniform thickness if a roller, such as indicated at 25, is used. This roller is tted with a handle 26 by which it may be moved back and forth over the top of the mass of material 24 and will act 'to level off the mass as Well as to compact the immediate top surface of the mass by reducing the size of the foramina in said surface mass. This is necessary due to the fact that the gas generated within the mass tends to form larger ioramina near the top of the mass. When the slab sets under this condition there will not be a uniform distribution of cementitious material throughout the mass. with the result that the density of the slab will not be uniform and the slab will warp unless the foramina in thetop surface mass are reduced to a size substantially agreeing with that of the opposite side. The warping action referred to is -produced by unequal shrinking of the sides of the slab with relation to each other. It will thus be evident that in addition to leveling the mass at a consistency which it possessed when withdrawn from the expansion kiln Il the material will be compressed so that the product will be more dense and will be of uniform porosity, texture and strength. This rolling action will also compress the mass and reduce the size of the foramina throughout the mass, thus increasing the strength and insulation. As a series of forms I are leveled oil they are placed upon trucks I3' which are upon a track I2'. This track extends through a drying kiln 21, after which it is carried to an unloading platform at the exit end of the drying kiln. A cable 28 is led around pulleys 29 and 30 at the opposite ends of the track section I2'. This cable may be engaged by a gripping device 3i so that the truck I3' will travel with the cable. A suitable driving means 32 is associated with the pulley 29 so that the cabl'e'28 may be drawn through the drying kiln 21 at any desired rate of speed. The purpose of the drying kiln 21 is to finally drive oilr the water from the mass of cement and to cure the cement so that it will be strong. The drying kiln 21 has two heating zones in it. The one at the forward end of the kiln is heated by live steam. This steam is introduced from a suitable source through coils 33 which are placed along the opposite side walls of the tunnel through the kiln. These vcoils are perforated so that live steam will be discharged into the forward end of the kiln 21. Itis desired that a plurality of forms I5 with the cementitious product therein are stacked on each of the trucks I3 and I3 and are held in vertical spaced relation by supporting members 34 and spacers 34. Thus, as a stack of forms is carried in the kiln 21 there will be an opportunity for the steam and heated air to pass entirely around the different forms. This insures that they will be dried uniformly. It is to be understood that a vertical partition 21 divides the kiln 21 so that the steam and heating chambers will be separated substantially. At the exit section of the kiln 21 heated air is delivered from a suitable source through a conduit 3| to a distributing passageway 35. This passage is beneath the track I2 and thus permits the air to pass up and around the forms on the trucks.A If desired a suitable flue may be connected to the kiln 21 so that the moist vapor may be drawn oi from the kiln as the drying operation progresses. 'I'he live steam which is introduced into the kiln 21 will be at the usual temperature at which steam forms and the heated air introduced will be at a desired temperature ranging from 100 to 250 F. It will be understood of course that the forms I5 carrying the cementitious slabs are allowed to remain within the kiln for a considerable period of time, depending upon the time required to cure the cement and the amount of heat applied.

It is contemplated that the panels or slabs of material cast within the forms I5 shall incorporate reinforcing material 36. This is preferably metal reinforcing mesh which is positioned substantially midway the thickness of the cementitious panels. In actual practice it has been found that while these sheets of mesh material were in the panel during the time it was drying and curing there was a tendency for the mass of cementitiousl material to crack in planes substantially normal to its surface and thus crosswise of the thickness of 'the panel and the reinforcing element 36. This action will of course be accelerated by forced drying and curing and in direct relation thereto. Due to this arrangement the reinforcing material acts as a binder to prevent the general mass from spalling, at the same time holding the slab together so that it will not shrink. It will thus have suitable tensile strength and a network of cracks 31 will occur over its entire surface to be used benecially in bonding cementitious coating surfaces to the panels 38.

After the panel 38 of expanded cementitious material has passed through the drying kiln 21 the forms I5 with the panels 38 therein are transported to a building site. 'During this transporting operation the panels are disposed in vertical position. The forms are removed from the panels after the panels have been disposed vertically and may then be placed in proper position within a building under construction. It will be recognized that the panels 38 may be lifted and moved by means gripping the upper edges of the panels, thus depending upon the reinforcing members 3B to provide suiicient strength for the p anels. When the panels are set in position a suitable coating 39 of cementitious material may be applied to the opposite sides thereof, although it is to be understood that the panels may receive this coating at the plant before being transported for use. This coating may be applied by troweiing or by the use of pneumatic placement means. It will be recognized that the cementitious outer coating 39 will be forced into the cracks 31 in the outer surfaces of the panel 38 so as to form a bond therewith. It is also tov be pointed out that since some building ordinances require that pre-cast panels shall be covered with a coating of waterproofing material this may be applied directly to the panels 38 or on the outside of the cement coating 39. When applied directly to the panels 38 the bonding action will not be impaired due to the cracks which have been formed in the surface thereof.

From an analysis of the foregoing description and the accompanying drawings it will be seen that a mass of cementitious material including light-weight aggregate may be formed into a slab or core member within which reinforcing means are imbedded, or that an expanded mass of foraminous cementitious material may be used and treated by the drying method here disclosed, so that a core will be produced having definite tensile strength and side surfaces having fissures or crevices therein to receive a coating of paint, waterproofing material or the like, or to receive bonding portions of cementitious coatings which have sufficient strength to resist lateral compression. It will be evident further that a panel or wall structure of the character here described will be provided having a transverse section somewhat similar to an I-beam, since the light-weight and relatively weak core is comparable to the web of an I-beam, and the outer relatively dense and strong cementitious coatings are comparable to the faces or flanges of an I-beam, thus insuring a structural panel which will have suitable tensile and compression strength, and will at the same time possess the necessary heat-insulating properties.

It will thus be seen that the cementitious building element here disclosed and a method of forming the same insures that light-weight building panels will be provided having a heat-insulating core and strengthening outer coating to produce a relatively thin cementitious panel having sufficient heat-insulating properties and strength to be used satisfactorily in the construction of various types of buildings.

While I have shown the preferred form of my building element and the preferred method and means for making the same. it is to be understood that various changes might be made in the composition and construction of the building element, the apparatus for making the same, and changes in the steps of procedure also might occur to those skilled in the art. without departing from the spirit of the invention as claimed.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A method of making a cementitious slab for use in wall structures, which consists in preparing a cementitious mix including gas-evolving elements acting to form foramina throughout the mass, thereafter depositing a quantity of said mix in a form which defines the perimeter of a panel and is disposed horizontally and within which form reinforcing elements are disposed horizontally, then placing said filled form within an expansion chamber where heat is applied beneath the form whereby the action of the gas-evolving element will be accelerated to expand the cementitious mass to a volume greater thanA that required in the final panel, then removing the form and passing a roller over the surface thereof to compact the mass of material and to reduce and make substantially uniform the sizes of the foramina therein, then placing the form containing the mass of material within a drying and curing chamber within which the action of heat accelerates the drying and curing whereby the mass of cementitious material will set and will check and crack to form fissures in the mass substantially normal to the plane of the reinforcing material, then placing the panel in a vertical position and applying a`coating of cementitious material to the opposite surfaces thereofv and within the fissures whereby the panel will be given lateral stability.

2. A method of making a cementitious slab for use in wall structures, which consists in preparing a cementitious mix including gas-evolving elements acting to form foramina throughout the mass, thereafter depositing a quantity. of said mix in a form which defines the perimeter of a panel an'd is disposed horizontally and within which form reinforcing elements are disposed horizontally, then placing said filled Vform within an expansion chamber where heat is applied beneath the form whereby the action of the gasevolving element will be accelerated to expand the cementitious mass to a volume greater than that required in the final panel, then removing the form and passing a roller over the surface thereof to compact the mass oi' material and to reduce the sizes of the foramina therein as weil as reduce thev mass to a desired thickness, then placing the form containing the mass of material within a drying and curing chamber, thereafter subjecting the panel to the action of live steam, then subjecting it to the action of dry heat whereby the mass of cementitious material will set and will check and crack to form fissures in the mass substantially normal to the plane of the reinforcing material.

3. A method of making a cementitious slab for use in wall structures. which consists in preparing a cementitious mix cluding gas-evolving elements acting to form foramina throughout the mass, thereafter depositing a quantity of said mix in a form which defines the perimeter of a panel and is disposed horizontally and within which form reinforcing elements are disposed horizontally, then placing said lled form within an expansion chamber where heat is applied beneath the form whereby the action of the gasevolving element will be accelerated to expand the cementitious mass to a volume greater than that required in the final panel, then removing the form and passing a roller over the surface thereof to compact the mass of material and to reduce the size of the foramina therein as well as reduce the mass to a desired thickness, then placing the form containing the mass of material within a drying and curing chamber, thereafter subjecting the panel to the action of live steam, then subjecting it to the action of dry heat whereby the mass of cementitious material will set and will check and crack to form fissures in the mass substantially normal to the plane of the reinforcing material, then placing the panel in a vertical position and applying a coating of cementitious material to the opposite surfaces thereof and within the fissures whereby the panel will be given lateral stability.

HAL B. HAYES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Design and Control of Concrete Mixtures, ninth edt., -published by Portland Cement Association. (Copy in Division 15.) 

